The invention relates to copolymers comprising carboxylic acid groups, sulfo groups and polyalkylene oxide groups, and to the use thereof as a scale-inhibiting additive to washing and cleaning products, especially to phosphate-containing and phosphate-free detergent formulations for machine dishwashing.
Machine dishwashing should deliver the washed dishes in a residue-free cleaned condition with a faultlessly shiny surface, for which a detergent, a rinse aid and regenerating salt for water softening typically have to be used. “3 in 1” dishwasher detergents were introduced to the market in 2001 and combine the functions of detergent, rinse aid and regenerating salt in one product. In addition to detergent components for removal of the soiling on the ware, they comprise integrated rinse aid surfactants which ensure that water runs off the whole area of the ware during the rinsing and drying cycle, thus preventing scale and water spots. In addition, they comprise components for binding of the hardness-forming calcium and magnesium ions. As a result, there is no need for the consumer to replenish rinse aid and salt in the machine dishwasher. The incorporation of further functions (for example protection from glass corrosion and protection from the tarnishing of silver) led to the development of x in 1 (where, for example, x=6 or 9) or “all in one” products.
Copolymers composed of carboxyl-containing and sulfo-containing monomers have been an important part of phosphate-containing and phosphate-free machine dishwashing detergents for many years. However, the contribution that they make to the detergent and rinsing performance and in particular the contribution that they make to the prevention of scale on the ware is still in need of improvement.
EP-A 0 778 340 describes the use of copolymers of allyl alcohol ethoxylates and acrylic acid in phosphate-free dishwasher detergent compositions.
WO 02/08527 discloses sulfo-containing copolymers, the preparation of the copolymers and the use thereof as an additive to washing, cleaning and rinse aid products. The copolymers comprise (a) 70 to 100 mol % of at least two different monoethylenically unsaturated carboxylic acid monomers and (b) 0 to 30 mol % of one or more nonionic monomers. The sulfo groups are introduced by amidation with an amino-C1-C2-alkanesulfonic acid.
WO 2005/042684 describes the use of specific copolymers of acrylic acid, methacrylic acid and acrylic acid alkoxylates as scale-inhibiting additives in machine dishwashing.
DE 102 25 794 describes the use of sulfo-containing copolymers formed from 30 to 95 mol % of a monoethylenically unsaturated carboxylic acid, 3 to 35 mol % of at least one sulfo-containing monomer and 2 to 35 mol % of a (meth)acrylic acid alkoxylate as a scale-inhibiting additive to washing and cleaning products. In the examples, copolymers formed from (meth)acrylic acid, methoxy polyethylene glycol methacrylate and sulfoethylmethacrylic acid sodium salt are used. In a further example, a binary copolymer formed from acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid is used.
WO 2008/132131 describes the use of sulfo-containing copolymers formed from 30 to 95 mol % of acrylic acid and/or methacrylic acid, 3 to 35 mol % of a sulfo-containing monomer and 2 to 35 mol % of a nonionic monomer of the formulaH2C═C(R2)—COO—R3—[—R4—O—]n—R5 as a scale-inhibiting additive to machine dishwasher detergents for prevention of the formation of calcium phosphate deposits.
WO 2010/024468 describes the use of copolymers formed from a carboxylate-containing monomer, a sulfonate-containing polymer and an allyl ether or allyl alcohol ethoxylate with 1 to 5 ethylene oxide groups as an additive to washing and cleaning products. A preferred sulfonate-containing monomer is 2-hydroxy-3-allyloxypropanesulfonic acid.